Some valvetrains include lifters that pass through a cylinder head to transmit force from a cam positioned under the cylinder head to a rocker arm position above the cylinder head. The lifter may include a roller follower that abuts and follows the cam and a cylindrical portion that reciprocates within a bore in the cylinder head.
An anti-rotation guide may be used to maintain proper orientation of the roller-follower with respect to the cam. Examples of anti-rotation guides include a framing member positioned above the cylinder head and a pin and groove arrangement within the cylinder head. These designs may not always be reliable over the life of an engine. There continues to be a long felt need for anti-rotation guides that are compact, easy to manufacture, and highly reliable.